Bridge foundation depth measurement and safety diagnosis method using multiple laser beams and GPS information

Abstract

The present invention relates to a method for measuring the depth of a bridge structure and diagnosing safety using multiple laser beams and GPS information. More specifically, it relates to an improved method for measuring the depth of a bridge structure and diagnosing safety using multiple laser beams and GPS information, which precisely acquires the shape of a bridge substructure through multiple laser scanning data and fuses GPS-based position information to calculate the foundation depth (depth) of the structure with high precision, while simultaneously analyzing displacement and stability over time in real time.

Description

Technology Field

[0001] The present invention relates to a method for measuring the depth of a bridge structure and diagnosing safety using multiple laser beams and GPS information. More specifically, it relates to an improved method for measuring the depth of a bridge structure and diagnosing safety using multiple laser beams and GPS information, which precisely acquires the shape of a bridge substructure through multiple laser scanning data and fuses GPS-based position information to calculate the foundation depth (depth) of the structure with high precision, while simultaneously analyzing displacement and stability over time in real time. Background Technology

[0002] Ensuring the safety of bridge structures is a critical factor in the maintenance of social infrastructure, and in particular, the foundation depth is a key element directly linked to structural stability.

[0003] Traditionally, direct measurements using divers or acoustic surveys have been primarily used to measure the depth of bridge foundations.

[0004] However, this method relies heavily on the measurement environment, and worker safety issues always exist.

[0005] In particular, in river or marine environments, it is difficult to secure visibility, and there is a problem where measurement accuracy is significantly reduced depending on the flow velocity and turbidity.

[0006] Furthermore, acoustic-based measurement technology has limitations in accurately measuring bottom depth due to distortion of reflected signals caused by seabed or riverbed conditions.

[0007] Existing laser-based measurement technologies have been primarily applied to terrestrial structures, and their application in underwater environments has been limited due to laser attenuation and scattering.

[0008] Furthermore, while GPS-based positioning technology is useful for providing location information, it has limitations in measuring the precise shape or depth of structures on its own.

[0009] Existing technologies have the problem of poor data consistency and difficulty in real-time analysis when used individually.

[0010] Furthermore, proactive maintenance is difficult due to the lack of an integrated analysis system to track bridge deformation or settlement over the long term.

[0011] Therefore, new technology capable of simultaneous high-precision measurement and real-time safety diagnosis is required. Prior art literature

[0012] Republic of Korea Patent Registration No. 10-0874879 (December 12, 2008) 'Method for Safety Diagnosis of Bridge Pier Structures' The problem to be solved

[0013] The present invention has been devised to solve the problems of the conventional technology described above, and aims to provide a method for measuring the depth of a bridge structure and diagnosing safety using multiple laser beams and GPS information, which enables high-precision calculation of the depth of a bridge foundation by using multiple laser beams to precisely scan the shape of the lower part of a bridge structure and fusing GPS information to accurately align spatial coordinates, and enables safety evaluation by analyzing positional changes and structural deformation over time in real time. means of solving the problem

[0014] The present invention provides a method for measuring the depth of a bridge structure and diagnosing safety using multiple laser beams and GPS information, characterized by comprising the steps of: acquiring three-dimensional point cloud data of the lower part of a bridge structure using multiple laser beams to achieve the above-mentioned purpose; forming an absolute coordinate system by combining GPS-based position information with the point cloud data; calculating the depth of the bridge structure by calculating the lowest point based on the coordinate data; and evaluating the stability of the structure by analyzing the change in the depth of the bridge structure over time. Effects of the invention

[0015] According to the present invention, by fusing multiple laser beams and GPS information, the three-dimensional shape of a bridge substructure can be obtained with high precision, and the measurement accuracy is improved compared to the existing method.

[0016] In addition, real-time data processing enables continuous monitoring of structural displacement and settlement, allowing for early risk detection.

[0017] In addition, safety is enhanced as remote measurement is possible without direct worker access, and maintenance efficiency is significantly improved as data-based quantitative safety diagnosis is enabled. Brief explanation of the drawing

[0018] FIG. 1 is a flowchart illustrating a method according to the present invention. Specific details for implementing the invention

[0019] Hereinafter, preferred embodiments according to the present invention will be described in more detail. Prior to describing the present invention, the following specific structural or functional descriptions are merely illustrative examples of embodiments according to the concept of the present invention in various forms and should not be interpreted as being limited to the described embodiments.

[0020] The method for measuring the depth of a bridge structure and diagnosing safety using a plurality of laser beams and GPS information according to the present invention comprises: a step of acquiring three-dimensional point cloud data of the lower part of a bridge structure using a plurality of laser beams as shown in the example of FIG. 1; a step of forming an absolute coordinate system by combining GPS-based position information with the point cloud data; a step of calculating the depth of the bridge structure by calculating the lowest point of the bridge structure based on the coordinate data; and a step of evaluating the stability of the structure by analyzing the change in the depth of the bridge structure over time.

[0021] More specifically, the method for measuring the depth of a bridge structure and diagnosing safety using a plurality of laser beams and GPS information according to the present invention performs the following steps.

[0022] (1) Laser scanning data acquisition step

[0023] Multiple laser beams are irradiated onto the underside of the bridge structure to receive reflected signals, thereby generating three-dimensional point cloud data.

[0024] At this stage, the distance di of each laser beam is calculated as follows.

[0025]

[0026] Here, c: speed of light, t i : Round-trip time of the i-th laser

[0027] For example, the speed of light c = 3 × 10⁻⁶ 8 m / s, round trip time ti=10 -7 If it is s

[0028] di=(3×10 8 ×10 -7 ) / 2 = 15m

[0029] In other words, the distance to that point is calculated as 15m.

[0030] (2) GPS-based position matching step

[0031] GPS coordinates are combined with each laser data to form an absolute position coordinate system.

[0032] Coordinate transformation is expressed as follows.

[0033]

[0034] Here,

[0035]

[0036] The second step, the GPS-based position matching step, is intended to compensate for the limitation that the point cloud data acquired in the laser scanning step is expressed in a relative coordinate system based on the laser equipment; it is an essential process for ensuring spatial consistency by converting the point cloud data into an absolute coordinate system based on the Earth.

[0037] In other words, since data acquired through laser scanning includes relative positional information dependent on the position and orientation of each measuring device, using this data as is makes it difficult to accurately determine the correspondence with the actual location of the bridge structure, and poses a problem in aligning data acquired from different locations or viewpoints.

[0038] Accordingly, in the second step above, absolute position information of the measuring equipment is obtained using GPS, and by combining this with the laser point cloud data, all measurement data are aligned on the same reference coordinate system.

[0039] Through this, even data acquired from multiple laser beams or multiple measurement points can be composed into a single integrated three-dimensional spatial model, and the problem of positional inconsistency between data can be resolved.

[0040] Furthermore, since the depth of a bridge structure is calculated based on the height difference between the lowest point and the reference plane, it is essential that the reference plane and the structure's location be defined in the same absolute coordinate system; therefore, the aforementioned GPS-based alignment step plays a crucial role in ensuring the accuracy of this depth calculation.

[0041] Furthermore, the aforementioned GPS-based position matching enables the comparison of repeated measurement data over time, allowing for the quantitative analysis of changes such as settlement, scour, or displacement of bridge structures; consequently, it provides the effect of enabling the long-term stability assessment and proactive maintenance of the structure.

[0042] Therefore, the aforementioned second step can be considered a key component for ensuring the consistency, reliability, and usability of measurement data, going beyond simple coordinate transformation.

[0043] To explain an example of calculating the above formula under this concept, if the GPS coordinates are (100, 200, 50) and the laser relative coordinates are (5, -3, -10), it can be expressed as Pi=(105,197,40).

[0044] (3) Low-depth calculation step

[0045] The lowest point coordinates are extracted from the collected point cloud data to calculate the depth of the base.

[0046]

[0047] At this time, D is the lower center, is the height of the water surface or reference plane, represents the height of the lowest point.

[0048] Therefore, for example, if the water level is 50m and the lowest point is 20m, the depth D = 50 - 20 = 30m.

[0049] Here, the third step, the depth calculation step, is a key step for quantitatively evaluating the structural stability of a bridge foundation by extracting the coordinates of the lowest point under the bridge structure from GPS-based aligned 3D point cloud data and calculating the depth relative to the reference plane.

[0050] Specifically, the safety of bridge structures is directly affected by the embedment depth and scour condition of the foundation, and foundation depth is one of the most important physical quantities for determining such structural soundness.

[0051] Therefore, in the above step, it is important to go beyond simple shape acquisition and reliably derive information on the lowest point of the structure and calculate the absolute depth value by comparing it with a reference plane.

[0052] In particular, the above step includes a process of removing noise from high-density point cloud data acquired through multiple laser beams and accurately identifying the geometric lowest point of the actual structure, thereby having the effect of minimizing errors that occurred in existing limited measurement point-based methods.

[0053] In addition, since the above-mentioned depth calculation is calculated using the difference between the reference plane height and the lowest point height defined in the same coordinate system, it can provide consistent results that are not affected by the measurement environment or equipment location, and ensures versatility applicable to various bridge environments.

[0054] Furthermore, the depth value calculated in the above step is not limited to identifying the state at a single point in time, but can be combined with data on changes over time to be utilized as basic data for early detection of scour progression, settlement rate, and signs of structural anomalies.

[0055] Furthermore, the above-mentioned bottom depth calculation results can be used to evaluate the safety margin by comparing them with the design standard bottom depth, or as a criterion for determining the timing of maintenance and reinforcement, thereby contributing to the systematic maintenance and lifespan prediction of bridge structures.

[0056] Therefore, the aforementioned third step is not a step of performing simple distance calculations, but a step of deriving key indicators to quantitatively evaluate the safety of the bridge structure.

[0057] (4) Safety evaluation stage

[0058] Stability is determined by analyzing the rate of change in depth over time using the equation below.

[0059]

[0060] Here, R: rate of change of depth, D t : Current low heart, D t-1 : Previous lower heart

[0061] For example, previous low depth is 30m, current low depth is 32m, time is 1 month → R=2m / month

[0062] This means that erosion or subsidence is in progress.

[0063] The fourth step, the safety evaluation step, is a step for quantitatively determining the structural stability of a bridge structure by comparing and analyzing the depth values ​​derived from the depth calculation step over time.

[0064] Specifically, the foundation of a bridge structure can continuously change due to various external forces such as scour, settlement, and loss, and it is difficult to accurately assess these changes based solely on measurements from a single point in time. Therefore, in the above step, the stability of the structure is evaluated by analyzing the amount and rate of change over time based on depth data calculated at multiple points in time.

[0065] In particular, since the increasing or decreasing trend of the base depth directly reflects the state of erosion or sedimentation of the foundation ground, the analysis of the above rate of change can detect early signs of scour progression, settlement rates, and abnormal deformation.

[0066] In addition, the above step can be configured to go beyond simple numerical comparison and determine the risk level of the structure by comparing it with preset thresholds or risk criteria, and this can be utilized to generate a warning signal or determine the timing for maintenance.

[0067] In addition, the aforementioned safety evaluation step utilizes data aligned in a GPS-based absolute coordinate system, thereby minimizing errors caused by changes in measurement location or environment and ensuring the reliability of long-term monitoring data.

[0068] In addition, in the present invention, after the (2) GPS-based position matching step, a ‘dynamic weight-based point cloud data refinement (Point Cloud Refinement) step’ can be further performed to increase the reliability of the calculated absolute coordinate data.

[0069] For example, since the measurement environment beneath a bridge is highly likely to contain outliers due to diffuse reflection from the water surface or floating debris, simply extracting the lowest point may result in such noise being mistaken for the lowest point, leading to errors in depth calculation. To prevent this, reliability weights (Wi) are assigned to each point cloud data (Pi) by analyzing its density and continuity with surrounding data, and data below a certain threshold can be excluded.

[0070] At this time, the confidence weight Wi of each point Pi can be defined as follows.

[0071]

[0072] Accordingly, if a specific laser point (Pi) is the average position of surrounding points ( If it is far from ) (i.e., if it is isolated noise), As the value increases, the weight Wi converges to 0.

[0073] On the other hand, in areas where points are densely packed, such as on the walls or floors of structures, the numerator value becomes smaller, and Wi approaches 1.

[0074] The present invention fundamentally prevents measurement errors caused by surface reflections or temporary floating objects by excluding data with Wi < 0.5 from the depth calculation target.

[0075] That is, the above additional step goes beyond simple coordinate transformation and includes a process of reviewing the statistical significance of the data to select only valid structural coordinates, thereby preventing the 'misidentification of the lowest point' that may occur during depth calculation and providing the effect of significantly improving the precision of the final safety assessment results.

Claims

Claim 1 delete Claim 2 A method for measuring the depth of a bridge structure and diagnosing safety using multiple laser beams and GPS information, characterized by comprising: a step of acquiring three-dimensional point cloud data of the lower part of a bridge structure using multiple laser beams; a step of forming an absolute coordinate system by combining GPS-based position information with the point cloud data; a step of calculating the depth of the bridge structure by calculating the lowest point based on the data of the absolute coordinate system; and a step of evaluating the stability of the structure by analyzing the change in the depth of the bridge structure over time; wherein the depth of the bridge structure is the difference between the height of a reference plane and the height of the lowest point. (D is the center, is the height of the water surface or reference plane, is calculated as the height of the lowest point; the above safety evaluation is the rate of change in depth over time (R: Rate of change in depth, D t : Current low heart, D t-1 : Performed using the previous depth), and to enhance the reliability of the absolute coordinate system data, an additional 'Dynamic Weight-Based Point Cloud Refinement Step' is performed, wherein for each point cloud data (Pi), the density and continuity with surrounding data are analyzed to assign a reliability weight (Wi), and data below a certain standard is excluded, and at this time, the reliability weight Wi of each point cloud data (Pi) is A method for measuring the depth of a bridge structure and diagnosing safety using multiple laser beams and GPS information, characterized by being calculated as follows.

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